Flare System Design: A Case for Dynamic Simulation

Dynamic analysis and optimization of flare network system for topside process of offshore plant

Three flare systems are modeled and total plant depressurization is investigated using dynamic simulations in order to access the debottlenecking potential. Usually steady-state simulation of the flare network is used for sizing and rating of the flare system. By using dynamic simulations effects from line packing in the flare system can be studied. The results show that peak flow during a dynamic simulations is significantly lower than the peak flow used in a steady-state case. The three systems investigated span a wide range in flare system size, both in terms of number of process segments disposing into the flare network, in terms of peak design rate and the flare network pipe dimensions and total hold-up volume. Generally, it is observed that the larger the flare system, the larger debottlenecking potential.

Heat integration is commonly skipped when evaluating a process' relief systems design. Failing to evaluate the heat integration (or energy balance) for a process can result in overly conservative results and possibly lead to costly expenditures. Evaluating the effects of heat integration in relief systems design is a process that evaluates the physical limitations of the system and does not require taking credit for control system response. It is important to understand the effects that heat integration has on both individual relief devices, and in some cases, the significant affect it can have on flare system design. This becomes even more imperative in cases where relief devices that once discharged to the atmosphere are modified to discharge into a closed flare system. This article covers two examples where evaluating the effects of heat integration on the relief systems prevented costly modifications to those systems. © 2013 American Institute of Chemical Engineers Process Saf Prog, 32: 244–247, 2013

Hydrocarbons and Acid gases flares are common in Oil and gas processing plants. Main flame extinguishment is encountered as major concern in these flares due to the inability to re-ignite the main flame through pilots. This can result in serious HSE concern by release of toxic (H2S) and hazardous hydrocarbon into environment, causing harm to people and surrounding. This paper presents the approach followed in flare system design which will enhance reliability of flare system for safe plant operation. Main issues in flares such as main flame extinguishment, failure of pilot, damage and burn of pilot, failure of thermocouples and blockage of pilot gas lines / fire ball lines were studied. All past inspection reports were reviewed to identify failure mechanism. Further aerial survey report were also reviewed. As flare pilots are exposed to severe operating temperature and service conditions, detail metallurgical study was performed to understand high temperature sulphidation corrosion. As existing flare were with old design, new technologies were explored and gap in current flare design were identified. Material review concluded that existing Inconel material will prematurely fail in high temperature acidic environment. Hence new pilot assembly and flare tip of SS310S material were installed. To further enhance service life, Pilots were ceramic coated and thickness of pilot /FFG pipe were increased. Wind proof pilot design with weather hood and integral thermowell in single cast assembly were used to minimize welding. This approach avoided weld failures in the Pilot which have been observed earlier. Flare tip are provided with wind shields to minimize impact due to flame impingement which damages the Pilot Assembly. Instead of existing single ignition and monitoring system, Dual Ignition through High Energy ignition and FFG & dual monitoring System using ionization rod and thermocouple are provided to ensure availability in the event of a primary system failure. Above new design improvements were successfully implemented in two of the existing flares. Continuous monitoring of the improvements confirmed reliable performance with no flare system failure in past 1.5 years. This will reduce cost by almost 50% due to decreased maintenance and increased life span. Further, it will optimize shutdowns and increase major maintenance cycles from 2 to 5 years. Conventional approach of like to like replacement of flare system in case of failure do not address the issue and can affect people, plant and environment. However, implementation of the design improvements based on above approach will not only ensure reliable and safe plant operation but also reduce maintenance cost.

The cooling water system consists of a mechanical draft cooling tower, cooling water circulation pumps and chemical treatment. Cooling water at 88/sup 0/F is pumped to distribution by the cooling water circulating pumps from the cooling tower through the supply header to users. From the users the cooling water (average temperature: 114/sup 0/F/design: 118/sup 0/F) completes the closed-loop system via the return header to the tower. The cooling water chemical feed system provides for automatic and continuous monitoring of circulating-water quality. The monitored water quality is used to control the sulfuric acid pump, corrosion inhibitor addition pump, dispersant addition pump, direct injection of gaseous chlorine and a cooling water blowdown valve. The blowdown controls total dissolved solids and pH and is sent to waste water treating for treatment. Other equipment associated with the cooling water is described. The primary source of makeup cooling water is city water from the Memphis Davis Pumping Station stored in the utility area. The flare system provides for the safe burning of combustible vapors released from process equipment during operating upset conditions, start-up and shut-down. The Elevated Flare System provides for smokeless burning of the hydrocarbon vapors by use of steam injection at the flare tip. The height and location of the flare are designed so that heat radiation will not be hazardous to personnel or equipment in the immediate vicinity.

The facilities associated with producing nonassociated gas from offshore fields consist of wellheads and tie-in platforms, which are equipped with flare systems. At wellhead platforms, the flares are maintained where a high integrity protection system (HIPS) is provided at each wellhead for over pressure protection. In addition, continuous flares are usually provided at tie-in platforms as another layer of protection. The initiative is to convert tie-in flares to maintenance, which will eliminate continuous flaring and further minimize the emissions. There are three protection layers consisting of Emergency Shutdown system (ESD) system, a HIPS system, and mechanical relief valves with partial flaring at the tie-in platforms, which activate in case both ESD and HIPS protection systems at the wellhead platform do not respond to an overpressure condition. Normally the original design will have the relief system and continuous flaring at the TPs manifolds as another protection layer. However, the HIPS design stated that the design shall ensure that HIPS alone bridges the safety risk gap. A methodology and comprehensive engineering assessment was conducted to evaluate the risk for modification of continuous flare to maintenance flare considered with partial flare and without partial flare. The study concluded that continuous flaring is no longer required and the HIPS alone is sufficient for over-pressure protection. This initiative will eliminate thousands of tons of CO2 emitted to the environment from the continuous flaring. The total cost savings analysis includes gas value creation and maintenance cost savings such as propane (fuel) burning reduction, flare tip replacements, and maintenance costs.

Developments in flare systems for the emergency de-pressurisation of oil production trains on offshore platforms in the North Sea are reviewed in terms of safety, efficiency, cost, installation and material usage. The most commonly used systems are enumerated and the fundamental requirements re-stated. Appraisal is made and notional costs given of each type cited. API guide RP521 rules for the calculation of radiation and temperature levels are examined and the extrapolations to them required for use on North Sea platforms stated. Structural prob1ems in the design of lightweight structures subject to ice and high wind loadings are examined with regard todynamic analysis of individual members.consideration of wake induced forces and shielding.the derivation of wind force spectrum from considerations of wind structures for inclusion in a dynamic analysis of complete structuresselection of heat resistant materials in locations near the heat source INTRODUCTION The exploitation of oil fields in the North Sea has led to situations which the generally adequate design guidance given in the API guide for pressure relief and de-pressuring systems (RP521) does not cover specifically. Its intent has therefore been extrapolated in various ways and the object of this paper is to review and to make a personal appraisal of what has been done to date with regard to one aspect, namely the positioning of burners and the concomitant structure which supports the gas lines to the burners. The main special circumstances in the North Sea which have influenced facilities design are as follows:In deep, storm prone, waters economics dictated that complete facilities be provided on single platforms. Where pipelines to shore were not possible these facilities had to include storage in addition to drilling, primary separation and production.On single platforms the separation of hazardous areas from accommodation and communication areas could no longer be achieved by separate platforms inter-connected with bridges but had to be by fire barriers dividing a single platform. This necessitated that either the gases to be burnt were taken directly from the process area and flared from near that hazardous area on the platform or the gases were conducted away by sub-sea line to a stack mounted on a secondary p1atform or swivelling buoy remote from the main structure. For shallow, calm water the remote stack solution combines safety with economy. For deep, rough water maintenance problems concerned with purging accumulations of condensate in the sub-sea line and igniters and pilots sharply reduce safety standards, while the placing of the lines and remote stacks in depths of water up to 150 metres multiplies the minimum cost by a factor of at least 8. A further complicating factor is that, due to the present climate of energy conservation, large volumes of gas are only flared in an emergency de-pressurisation or during commissioning of plant although the pressure relief system must assuredly be available for an emergency, it is otherwise lightly used. A system in frequent heavy use must be kept in efficient working order, one lightly used is liable to receive less attention.

First of all a reminder is given of the equations that describe the temperature increase with time of a reacting mass in adiabatic conditions. A discussion follows on the related plots, obtainable through tests with laboratory adiabatic calorimeters and pilot or industrial reactors, with particular reference to the problem of extrapolating to industrial reactors the results got through small apparatuses, primarily in the case of complex reactions as the phenol-formaldehyde one. The mechanisms of the two fundamental phases of this reaction (methylolation and condensation) are reminded, trying to correlate the total temperature increase (and therefore the overall heat of reaction) with the energy contributions of the single phases and with the molar ratio (formaldehyde/phenol) characterizing the reacting mixture. Then we report the calculation procedures suggested by DIERS for sizing emergency relief devices, with reference to the so-called “tempered” systems in which pressure and temperature are reciprocally correlated by the law of variation of the vapour pressure of the solvent (that is water in our case). For relief area evaluation we used the equation suggested by Leung supposing a two-phase homogeneous discharge flow (HEM). For determining the specific flow, including the reduction effect due to the pipe downstream the relief device, we used the “ω method” by the same Author. For the calculation of the reduction coefficient, which corrects the expression of flow through an ideal nozzle, we worked out some approximate simplified formulas, which apply to the most customary discharge configurations. An account follows of performed tests and used apparatuses, with the consequent working out of the results to obtain the thermokinetic constants (DH, E, K) characterizing the reaction of phenolic resins formation with basic catalysis. In particular we evaluated the influence of a variation of catalyst concentration around the values of normal use. At last we worked out a complete and detailed numerical example, studying the influence on the relief area both of rupture disk set pressure and reactor maximum allowable pressure, and of the possible inaccuracy which affects one of the thermokinetic parameters (DH). The example includes the evaluation of the thrust exerted on the discharge pipe and the preliminary sizing of the most suitable containment system for the emission. A mention is also made of the useful precautions to prevent or contain the quick temperature rise and so to avoid the rupture disk intervention.

The study presents a comprehensive analysis of the High Pressure (HP) Flare Header system, emphasizing its critical role in the safe management of hydrocarbon processing facilities. The study details the integration of the HP Flare Header with multiple upstream sources, addressing operational considerations such as back pressure issues due to flare tip design. It highlights the importance of maintaining system integrity under both routine and emergency conditions while ensuring compliance with industry safety and environmental standards. The analysis includes an overview of flare systems, their significance in safety and environmental protection, and the operational efficiency they provide. Special attention is given to sonic flares, their enhanced combustion efficiency, and the challenges associated with back pressure. The study proposes modifications to the existing flare tip design to mitigate back pressure issues, ensuring reliable performance and safety. The proposed modifications aim to improve back pressure management, enhance operational stability, and reduce greenhouse gas emissions, contributing to a more efficient and environmentally friendly flare system.

Based on the advantage of seamless integration between LMS Motion dynamics simulation module and CATIA, a prototype of the hinge arm of passenger airplane cabin door is established in CATIA, then dynamic simulation analysis is carried out in Motion. The results of Motion dynamics simulation can clearly reflect the change of Motion and force of the chain in the process of opening the door, which is consistent with the design expectation and test results, and it proves the rationality of the relevant treatment in dynamic simulation, and also demonstrates the effectiveness and convenience of LMS Motion in dynamic analysis.

An ethylene plant’s shutdown operations affect the recovery of production and material. Careless operations can lead to a great amount of material emissions that have to be sent to flare systems. Moreover, the flare systems discharge gaseous pollutants that inevitably damage the surrounding environment. The ethylene splitter system is the major part of an ethylene plant, and its operations can affect product quality. We make two primary contributions. First, we present an improved shutdown plan for an ethylene splitter system that aims at recovering more material and reducing flare emissions. The basic idea of the plan is using recycling streams to provide surge protection for the ethylene refrigerant compressors after stopping feeding. Meanwhile, gaseous ethylene in the system is recovered as much as possible and then sent to the adjacent ethylene plant or fuel system. Second, we develop a dynamic simulation model of the ethylene splitter’s shutdown process by using Aspen Dynamics. Then we present a flar...

Wang, G. and Zhang, Y., 2020. Dynamic simulation analysis of port economic throughput difference in marine environment. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 268–272. Coconut Creek (Florida), ISSN 0749-0208.A large number of sample data are needed in the dynamic simulation analysis of port economic throughput difference in the marine environment. In the traditional dynamic simulation method, the distribution of sample data is unbalanced, which affects the reliability of the simulation results. Therefore, the dynamic simulation analysis of port economic throughput difference in the marine environment is proposed. This paper analyzes the influencing factors of port economic throughput, determines the appropriate influencing factors by calculating the correlation coefficient, constructs the port economic throughput difference model, takes the predicted value and the original number series obtained by the model as the input, uses the trend extrapolation method and the linear regression model to realize the dynamic simulation of port economic throughput difference. The experimental results show that: compared with the traditional dynamic simulation method, the sample data of the dynamic simulation method of port economic throughput difference under the designed marine environment is evenly distributed, and this method is suitable for practical projects.

Restricting the lift of relief devices is seen as a solution to various challenges associated with installing pressure relief valves (PRVs), particularly in addressing high inlet pressure drops and meeting criteria set by standards such as API STD 520. Previous studies and industry presentations have suggested that restricted lift can mitigate issues related to oversized valves and excessive inlet losses. However, there is ongoing debate regarding its impact on PRV operational stability. This paper presents comprehensive test data showing that restricting the lift of a direct spring‐operated relief device does not improve valve stability in vapor/gas service. The data further indicate that stability is not influenced by the required relief rate. While restricted lift reduces capacity, it does not alter the valve's dynamic characteristics. These findings are consistent with earlier work reporting negligible effects on blowdown and valve performance when lift is restricted. Data from over 1500 tests suggest that the reduction in lift can help mitigate some negative system effects caused by valve instability. These results underscore the importance of understanding the trade‐offs involved in applying restricted lift as a strategy to address PRV installation challenges without assuming improved stability.

This paper presents application guidelines for a new generic plant controller model that can be used for renewable plant dynamic system analysis that may include the control of static compensators (STATCOMs), static var compensators (SVCs), and/or energy storage devices. The authors originally presented the need for such a model to the Western Electricity Coordinating Council (WECC) and contributed to various stages of the new model development led by WECC. As Independent System Operators (ISOs)/Regional Reliability Organizations (RTOs)/Transmission Service Providers (TSPs) are moving toward acceptance and use of generic models only the authors have for the first time applied this new model for an operating renewable plant. The new model was configured, parameterized, and tuned to control two STATCOMs and multiple switched capacitors/reactors to represent a master/auxiliary control strategy as implemented in the plant. Dynamic simulations show that the configured and parameterized model is performing properly as expected. This tuned model was submitted to the system operator for compliance with the interconnection requirements of the plant. This is the first submission of the new generic model for this type of control for a renewable project. The submitted model is appropriate for dynamic simulations, which are routinely performed by ISOs/RTOs/TSPs in system impact studies or transmission planning studies. This paper provides useful guidelines in applying this new model for similar projects.

Aiming at the Megawatt (MW) scale wind turbine, a dynamic analysis and simulation method is presented to research blade loads and dynamic characteristics. To consider blade flexible deformation, the whole blade was divided into a number of units. Each unit was treated as a rigid body, the flexible connection between two adjacent units is considered. A nacelle coordinate system, a rotating shaft coordinate system, and a blade coordinate system were employed to describe the wind turbine blade. In those coordinate systems, blade inertial load calculation model, centrifugal force load calculation model and gravity load calculation model are established. Combining load model with the whole model of wind turbines, the real-time dynamic simulation model of blade loads was established in Simulink circumstance and a numerical simulation was performed. Based on the simulation analysis, some research results were obtained. When the large instantaneous fluctuation of electromagnetic torque of generator happens, rotor speed does not appear to have large fluctuation due to the inertia of the wind rotor, but the blade vibration speed changes obviously. Gravity has a periodic variation in the process of blade rotation and has a large influence on the edgewise moment. The research results provide a helpful reference for the structure design, operation, and control of wind turbines.